Gammon Forum

/*
 * Check hash table for existing occurance of string.
 * If found, increase link count, and return pointer,
 * otherwise add new string to hash table, and return pointer.
 */
char *str_alloc( char *str )
{
   register int len, hash, psize;
   register struct hashstr_data *ptr;

   len = strlen( str );
   psize = sizeof( struct hashstr_data );
   hash = len % STR_HASH_SIZE;
   for( ptr = string_hash[hash]; ptr; ptr = ptr->next )
      if( len == ptr->length && !strcmp( str, ( char * )ptr + psize ) )
      {
         if( ptr->links < 65535 )
            ++ptr->links;
         return ( char * )ptr + psize;
      }
   ptr = ( struct hashstr_data * )malloc( len + psize + 1 );
   ptr->links = 1;
   ptr->length = len;
   if( len )
      strcpy( ( char * )ptr + psize, str );
/*     memcpy( (char *) ptr+psize, str, len+1 ); */
   else
      strcpy( ( char * )ptr + psize, "" );
   ptr->next = string_hash[hash];
   string_hash[hash] = ptr;
   return ( char * )ptr + psize;
}

/*
 * Used to make a quick copy of a string pointer that is known to be already
 * in the hash table.  Function increments the link count and returns the
 * same pointer passed.
 */
char *quick_link( char *str )
{
   register struct hashstr_data *ptr;

   ptr = ( struct hashstr_data * )( str - sizeof( struct hashstr_data ) );/* Line 107 */
   if( ptr->links == 0 )
   {
      fprintf( stderr, "quick_link: bad pointer\n" );
      return NULL;
   }
   if( ptr->links < 65535 )
      ++ptr->links;
   return str;
}

/*
 * Used to remove a link to a string in the hash table.
 * If all existing links are removed, the string is removed from the
 * hash table and disposed of.
 * returns how many links are left, or -1 if an error occurred.
 */
int str_free( char *str )
{
   register int len, hash;
   register struct hashstr_data *ptr, *ptr2, *ptr2_next;

   len = strlen( str );
   hash = len % STR_HASH_SIZE;
   ptr = ( struct hashstr_data * )( str - sizeof( struct hashstr_data ) );/* Line 131 */
   if( ptr->links == 65535 )  /* permanent */
      return ptr->links;
   if( ptr->links == 0 )
   {
      fprintf( stderr, "str_free: bad pointer\n" );
      return -1;
   }
   if( --ptr->links == 0 )
   {
      if( string_hash[hash] == ptr )
      {
         string_hash[hash] = ptr->next;
         free( ptr );
         return 0;
      }
      for( ptr2 = string_hash[hash]; ptr2; ptr2 = ptr2_next )
      {
         ptr2_next = ptr2->next;
         if( ptr2_next == ptr )
         {
            ptr2->next = ptr->next;
            free( ptr );
            return 0;
         }
      }
      fprintf( stderr, "str_free: pointer not found for string: %s\n", str );
      return -1;
   }
   return ptr->links;
}

hashstr.c: In function `quick_link':
hashstr.c:107: warning: cast increases required alignment of target type
hashstr.c: In function `str_free':
hashstr.c:131: warning: cast increases required alignment of target type